A variety of processes have been developed to remove toxic metals or radioactive materials from the environment or from wastes. This prevents such harmful materials from reaching the environment, and also sometimes allows for their recovery and reuse.
Chemical, physical and biological methods have been used to recover and/or flocculate toxic metals or to recover radionuclides from wastes or other sources. However, these methods are not very efficient. In order to function, the recovery agent must be in continuous contact with the contaminated substrate for a long period of time. Additionally, these methodologies are expensive and not cost-effective.
Chemical treatments, which are commonly used to recover toxic metals and radionuclides, may lead to greater environmental pollution because they are not biodegradable. Biological agents, such as chitosan, are normally used as single treatments and suffer from poor efficacy and inconstant results. Microbial treatments also suffer from inconsistency and poor efficacy because the microbes may lose viability due to toxic effects of the metals or radionuclides absorbed. Microbial treatments are also not able to produce flocculation of toxic metals. Absorption of radionuclides using biomass from dead microorganisms has also been unsatisfactory, producing only low levels of bio-absorption or bio-accumulation. Finally, physical treatments alone are expensive and are not practical when applied on large scaled demanded by many potential uses, especially with toxic metals. Additionally, common physical treatments do not produce flocculation of toxic metals.
Accordingly, a reliable, effective, cost-efficient method of removing toxic metals or radionuclides from waste or other sources is needed.